Displacement reactions as redox reactions
2 marks · EasyExplain, in terms of electron transfer, why bromine acts as an oxidising agent in its reaction with iodide ions.
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Bromine acts as an oxidising agent because it gains electrons from iodide ions. Bromine is reduced to bromide ions, while iodide ions are oxidised to iodine.
Must show: bromine gains electrons, bromine is reduced, iodide loses electrons
Also accept: bromine gains electrons from iodide ions; bromine is reduced as iodide is oxidised
Common mistakes: bromine loses electrons
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Marking points
M1 · 1 mark · States that bromine gains electrons (from iodide ions).
M2 · 1 mark · Links the electron gain to bromine being reduced / iodide ions being oxidised.
Worked solution
Bromine acts as an oxidising agent because it accepts electrons from the iodide ions.
Br2(aq) + 2I−(aq) → 2Br−(aq) + I2(aq).
The iodide ions lose electrons (are oxidised) and bromine gains electrons (is reduced).